Input devices including proximity sensor devices (also commonly called touchpads or touch sensor devices) are widely used in a variety of electronic systems. A proximity sensor device typically includes a sensing region, often demarked by a surface, in which the proximity sensor device determines the presence, location and/or motion of one or more input objects. Proximity sensor devices may be used to provide interfaces for the electronic system. For example, proximity sensor devices are often used as input devices for larger computing systems (such as opaque touchpads integrated in, or peripheral to, notebook or desktop computers). Proximity sensor devices are also often used in smaller computing systems (such as touch screens integrated in cellular phones).
Some input devices also have the ability to detect force applied to a sensing surface in addition to determining positional information. For example, Degner U.S. Patent Application Publication No. 2010/0079404 discloses an input device having a touch-sensitive track pad capable of detecting an X-Y position of an input object proximate the track pad, as well as a movement indicator for detecting movement of the movable track pad. Thus, a user can press down and “click” the pad to simulate a button press. FIG. 3B of Degner illustrates a clickable input pad configured for uniform translation; that is, the entire input surface deflects uniformly regardless of the X-Y location of the applied force. FIGS. 3C and 5 of Degner illustrate a hinged pad which pivots about a hinge, and deflects much like an aileron or door.
Both hinged and uniform clickable pads typically employ a mechanical or electronic switch, such as a rubber domed tach switch, to detect movement of the pad to perform a button click, as well as a spring mechanism to restore the pad to its original position following a button click. A typical resilient hinge for providing the restoring force is shown in FIGS. 6 and 28 of Degner.
Capacitive input devices in the form of a computer mouse are also known. For example, the Microsoft™ Arc Mouse and the Apple™ Magic Mouse employ a two-dimensional position sensor on the outside surface of a clickable mouse housing.
Presently known capacitive sensing mice utilize a single mechanical or electronic tach switch under a snap dome to detect a button press. When a finger is present on only the right button during a button press, the device indicates a right button press. Conversely, when a finger is present on only the left button during a button press, the device indicates a left button press. However, when two (or more) fingers are present on the sensing surface during a button press, the device is unable to determine whether the left or right button was intended, and therefore indicates a default button (typically a left button) press even though another button (e.g., the right button) may have been intended by the user. Consequently, it is difficult to determine which button (e.g., left or right) is pressed when multiple fingers are present.